Simple "Symbol" Type

Installing SymbolType (using "easy_installSymbolType" or
"setup.pyinstall") gives you access to the peak.util.symbols
module, previously available only by installing the full PEAK toolkit.
peak.util.symbols provides a Symbol type and two built-in symbols
that are used by PEAK: NOT_FOUND and NOT_GIVEN. You can create your
own symbol objects using the Symbol type, by giving it the symbol name
and the name of the module where the symbol is being created: